8,497 research outputs found
Symmetric and Asymmetric Asynchronous Interaction
We investigate classes of systems based on different interaction patterns
with the aim of achieving distributability. As our system model we use Petri
nets. In Petri nets, an inherent concept of simultaneity is built in, since
when a transition has more than one preplace, it can be crucial that tokens are
removed instantaneously. When modelling a system which is intended to be
implemented in a distributed way by a Petri net, this built-in concept of
synchronous interaction may be problematic. To investigate this we consider
asynchronous implementations of nets, in which removing tokens from places can
no longer be considered as instantaneous. We model this by inserting silent
(unobservable) transitions between transitions and some of their preplaces. We
investigate three such implementations, differing in the selection of preplaces
of a transition from which the removal of a token is considered time consuming,
and the possibility of collecting the tokens in a given order.
We investigate the effect of these different transformations of instantaneous
interaction into asynchronous interaction patterns by comparing the behaviours
of nets before and after insertion of the silent transitions. We exhibit for
which classes of Petri nets we obtain equivalent behaviour with respect to
failures equivalence.
It turns out that the resulting hierarchy of Petri net classes can be
described by semi-structural properties. For two of the classes we obtain
precise characterisations; for the remaining class we obtain lower and upper
bounds.
We briefly comment on possible applications of our results to Message
Sequence Charts.Comment: 27 pages. An extended abstract of this paper was presented at the
first Interaction and Concurrency Experience (ICE'08) on Synchronous and
Asynchronous Interactions in Concurrent Distributed Systems, and will appear
in Electronic Notes in Theoretical Computer Science, Elsevie
Effects of isospin and momentum dependent interactions on liquid-gas phase transition in hot asymmetric nuclear matter
The liquid-gas phase transition in hot neutron-rich nuclear matter is
investigated within a self-consistent thermal model using an isospin and
momentum dependent interaction (MDI) constrained by the isospin diffusion data
in heavy-ion collisions, a momentum-independent interaction (MID), and an
isoscalar momentum-dependent interaction (eMDYI). The boundary of the
phase-coexistence region is shown to be sensitive to the density dependence of
the nuclear symmetry energy with a softer symmetry energy giving a higher
critical pressure and a larger area of phase-coexistence region. Compared with
the momentum-independent MID interaction, the isospin and momentum-dependent
MDI interaction is found to increase the critical pressure and enlarge the area
of phase-coexistence region. For the isoscalar momentum-dependent eMDYI
interaction, a limiting pressure above which the liquid-gas phase transition
cannot take place has been found and it is shown to be sensitive to the
stiffness of the symmetry energy.Comment: 6 pages, 4 figures, revised version, to appear in PL
Acceleration effect of coupled oscillator systems
We have developed a curved isochron clock (CIC) by modifying the radial
isochron clock to provide a clean example of the acceleration (deceleration)
effect. By analyzing a two-body system of coupled CICs, we determined that an
unbalanced mutual interaction caused by curved isochron sets is the minimum
mechanism needed for generating the acceleration (deceleration) effect in
coupled oscillator systems. From this we can see that the Sakaguchi and
Kuramoto (SK) model which is a class of non-frustrated mean feild model has an
acceleration (deceleration) effect mechanism. To study frustrated coupled
oscillator systems, we extended the SK model to two oscillator associative
memory models, one with symmetric and one with asymmetric dilution of coupling,
which also have the minimum mechanism of the acceleration (deceleration)
effect. We theoretically found that the {\it Onsager reaction term} (ORT),
which is unique to frustrated systems, plays an important role in the
acceleration (de! celeration) effect. These two models are ideal for evaluating
the effect of the ORT because, with the exception of the ORT, they have the
same order parameter equations. We found that the two models have identical
macroscopic properties, except for the acceleration effect caused by the ORT.
By comparing the results of the two models, we can extract the effect of the
ORT from only the rotation speeds of the oscillators.Comment: 35 pages, 10 figure
Effects of isospin and momentum dependent interactions on thermal properties of asymmetric nuclear matter
Thermal properties of asymmetric nuclear matter are studied within a
self-consistent thermal model using an isospin and momentum dependent
interaction (MDI) constrained by the isospin diffusion data in heavy-ion
collisions, a momentum-independent interaction (MID), and an isoscalar
momentum-dependent interaction (eMDYI). In particular, we study the temperature
dependence of the isospin-dependent bulk and single-particle properties, the
mechanical and chemical instabilities, and liquid-gas phase transition in hot
asymmetric nuclear matter. Our results indicate that the temperature dependence
of the equation of state and the symmetry energy are not so sensitive to the
momentum dependence of the interaction. The symmetry energy at fixed density is
found to generally decrease with temperature and for the MDI interaction the
decrement is essentially due to the potential part. It is further shown that
only the low momentum part of the single-particle potential and the nucleon
effective mass increases significantly with temperature for the
momentum-dependent interactions. For the MDI interaction, the low momentum part
of the symmetry potential is significantly reduced with increasing temperature.
For the mechanical and chemical instabilities as well as the liquid-gas phase
transition in hot asymmetric nuclear matter, our results indicate that the
boundary of these instabilities and the phase-coexistence region generally
shrink with increasing temperature and is sensitive to the density dependence
of the symmetry energy and the isospin and momentum dependence of the nuclear
interaction, especially at higher temperatures.Comment: 21 pages, 29 figure
On the Distributability of Mobile Ambients
Modern society is dependent on distributed software systems and to verify
them different modelling languages such as mobile ambients were developed. To
analyse the quality of mobile ambients as a good foundational model for
distributed computation, we analyse the level of synchronisation between
distributed components that they can express. Therefore, we rely on earlier
established synchronisation patterns. It turns out that mobile ambients are not
fully distributed, because they can express enough synchronisation to express a
synchronisation pattern called M. However, they can express strictly less
synchronisation than the standard pi-calculus. For this reason, we can show
that there is no good and distributability-preserving encoding from the
standard pi-calculus into mobile ambients and also no such encoding from mobile
ambients into the join-calculus, i.e., the expressive power of mobile ambients
is in between these languages. Finally, we discuss how these results can be
used to obtain a fully distributed variant of mobile ambients.Comment: In Proceedings EXPRESS/SOS 2018, arXiv:1808.08071. Conference version
of arXiv:1808.0159
Patterns of consumption in a discrete choice model with asymmetric interactions
We study the consumption behaviour of an asymmetric network of heterogeneous
agents in the framework of discrete choice models with stochastic decision
rules. We assume that the interactions among agents are uniquely specified by
their ``social distance'' and consumption is driven by peering, distinction and
aspiration effects. The utility of each agent is positively or negatively
affected by the choices of other agents and consumption is driven by peering,
imitation and distinction effects. The dynamical properties of the model are
explored, by numerical simulations, using three different evolution algorithms
with: parallel, sequential and random-sequential updating rules. We analyze the
long-time behaviour of the system which, given the asymmetric nature of the
interactions, can either converge into a fixed point or a periodic attractor.
We discuss the role of symmetric versus asymmetric contributions to the utility
function and also that of idiosyncratic preferences, costs and memory in the
consumption decision of the agents.Comment: 11 pages, 9 figures, presented at "Complex Behaviour in Economics"
Aix-en-Provence 3-7 May, 2000. Minor modifications made: references added and
typos corrected. This paper is a fully revised version to the one previously
submitted as cond-mat/990913
Effects of non-resonant interaction in ensembles of phase oscillators
We consider general properties of groups of interacting oscillators, for
which the natural frequencies are not in resonance. Such groups interact via
non-oscillating collective variables like the amplitudes of the order
parameters defined for each group. We treat the phase dynamics of the groups
using the Ott-Antonsen ansatz and reduce it to a system of coupled equations
for the order parameters. We describe different regimes of co-synchrony in the
groups. For a large number of groups, heteroclinic cycles, corresponding to a
sequental synchronous activity of groups, and chaotic states, where the order
parameters oscillate irregularly, are possible.Comment: 21 pages, 7 fig
Non-catalytic bromination of benzene: a combined computational and experimental study
The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable (The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable (The non-catalytic bromination of benzene is shown experimentally to require high 5-14M concentrations of bromine in order to proceed at ambient temperatures to form predominantly bromobenzene, along with detectable
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